Scale formation is viewed as a persistent problem encountered in various industrial processes; it results in a significant reduction of the efficiency of these processes and the useful lifetime of the associated equipment. The challenges posed by scale formation have a significant impact on capital costs and operating costs.
Mineral scale deposits such as calcium sulfate are encountered in many industrial processes. These scales have low solubility limits, particularly at elevated temperatures (e.g., at or above 100° C.). Thus, processes involving boiling fluids may be even more affected by scale deposits, since scale forms more readily on surfaces, becomes thick, and adversely affects heat transfer and operability of the equipment.
Various surfaces have been developed for heat exchanger equipment to promote heat transfer; however, these surfaces are usually tested under ideal conditions: with deionized water with no scale deposition. In boilers and steam generation components, surface scale formation and fouling occurs such that over time a thick scale deposit will cover an initially scale-free surface. Scale is generally considered undesirable due to its low thermal conductivity. Thus, there is a need for improved surfaces and vessels to promote efficient heat transfer.
Certain conventional methods focus entirely on keeping as much scale as possible off of the surface by surface modification techniques for fouling mitigation or by using electric fields to inhibit scale formation. Yet, certain other conventional methods focus on mechanical removal of the entire scale deposition—for example, by injecting particles or using a mechanical part installed inside of a tube to scrape and clean away any scale buildup. These methods fail to appreciate the possibility of using the scale deposition to increase boiling heat transfer.
Certain conventional methods have tested data on surface scale formation and changes in heat transfer coefficient over time. However, these conventional methods fail to appreciate or contemplate controlling scale formation to enhance boiling heat transfer.
Other conventional methods relate to the effects of nanofluids on boiling heat transfer. These methods study the correlation between the deposition of nanoparticles from solution onto the surface and the rate of boiling heat transfer. These conventional methods fail to appreciate or contemplate using solution deposition as a method of enhancing heat transfer. Certain other conventional methods relate to the effects of depositing materials (e.g., nanoparticles) on the surface before boiling. Thus, conventional methods focus on direct texturing and treatment of surfaces before boiling to achieve heat transfer improvements.